Hemispherical Scanning Scatterometer Detector Segmentation
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Solution Overview
Problem
Current scatterometers fail to accurately measure light scattering over a complete hemisphere due to limited dynamic range and measurement speed, often missing data in both specular and non-specular regions, and are unable to cover the large dynamic range of optical surfaces.
Innovation Solution
A hemispherical scanning optical scatterometer using a scanning array of optical detectors with varying sizes and geometries to cover the complete hemisphere, allowing for rapid measurement with a dynamic range exceeding ten decades and increased measurement speed, capable of sampling both reflected and transmitted hemispheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single detector is used to scan through the hemisphere, then measurement speed is improved, but dynamic range is insufficient to handle scatter signals changing by more than seven orders of magnitude
Solution Approach 1:
The hemisphere is divided into multiple regions (specular region and non-specular regions) with different detector assignments. Small diameter detectors are used for the specular region where high resolution is needed, while larger detectors handle non-specular regions. This segmentation allows each detector to operate within an optimal dynamic range of about seven orders of magnitude, solving the contradiction between measurement speed and dynamic range coverage.
2Measurement precision
If multiple fixed detectors are used to sample hemispherical scatter, then dynamic range is improved, but device complexity increases and measurement speed decreases
Solution Approach 1:
Instead of using multiple fixed detectors, the patent employs a single moving detector that scans through the hemisphere. The detector is mounted on a rotation mechanism that allows it to move between specular and non-specular regions. This dynamic approach reduces device complexity compared to fixed multiple detector systems while maintaining the ability to cover the full dynamic range through sequential positioning.
3Measurement precision
If more measurements are made close to the specular beam, then measurement precision in specular region is improved, but measurement speed decreases due to time required for additional samples
Solution Approach 1:
The patent applies different detector characteristics to different regions of the hemisphere. Small diameter detectors with high angular resolution are positioned for the specular region where precise angular measurement is critical. Larger detectors are used for non-specular regions where the scatter signal is weaker and angular resolution requirements are lower. This local differentiation allows high precision near the specular beam without compromising overall measurement speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved hemispherical coverage, increased dynamic range, and faster measurement speeds, enabling accurate characterization of material properties such as surface roughness and optical characteristics like haze and transmittance, facilitating quality control and design processes.
Implementation Method 1
measures the intensity of light scattered by an object... the properties of the test sample will cause some portion of the light to be scattered in different directions known as scatter angles
Data Source
AI summary
A hemispherical scanning optical scatterometer and method for its use for measuring scattered radiation, with a reflected scatter measurement laser, and/or a transmitted scatter measurement laser, an array of optical detectors, a computer controlled system to rotate the array of optical detectors, an electronic system, a computer interface and a computer for processing the signal.